Food flavors contain both water soluble and oil soluble components. One of the problems in dispersing a flavor in cooking oils is the solubilization or dispersion of the oil insoluble component into the base product. If the oil insoluble component is volatile it will evaporate on storage. Other methods make heterogeneous solutions which separate or appear cloudy due to the dispersion. One way to add these flavorants or water soluble materials to an oil is through addition of emulsifiers. Emulsions of water and oil are thermodynamically unstable, tend to be milky and separate on standing. As the oil is heated the water evaporates as do the volatile water soluble components.
A specific type of water in oil solubilization which is thermodynamically stable is a microemulsion. Microemulsions are stable, clear liquids which are made of two phases, an oil and a polar solvent (e.g. water) and a surfactant. In many cases a cosurfactant or electrolyte or additional amphiphilic component is required for the formation of a microemulsion.
A clear oil which would contain these water soluble components in a stable form would be very useful. There have been a number of synthetic fuels developed which use vegetable oils and alcohol water solutions. These are formed as microemulsions through the use of high levels of monoglycerides and other co-surfactants. These microemulsions are optically clear, transparent and stable dispersions of oil, water, surfactant and co-surfactant mixed in specific proportions. However, their co-surfactants were unacceptable for food use.
Fat oxidation has been controlled through the use of ascorbic acid and alpha-tocopherol in a microemulsion consisting of soybean oil or sunflower oil, monoglycerides and water. The level of monoglycerides used range from 20% to 65%. This is high for a food product. Lee Moberger et al, J. Dispersion Science & Technology, 8 (3),207-215 (1987).
Essential oils have been added to foods and beverages in a microemulsion that uses a surfactant (HLB of 10 to 18) and an alcohol. (See U.S. Pat. No. 4,835,002) to Wolf et al (1989).
U.S. Pat. No. 4,568,480 to Dexheimer (1986) describes alkylated phenol derivatives for making microemulsions.
Accordingly, it would be desirable to provide a means for making water in oil mixtures in which the water was solubilized in the oil, the oil remained transparent or macroscopically homogeneous, and the water remains stable within the oil up to the boiling point of water. In addition, some of the water soluble flavor components remain in the oil when the oil is heated for a longer time than when there is no microemulsion present.
It is an object of this invention to provide such a system through the use of polyglycerol mono-diesters of an unsaturated or branched chain fatty acid having from 12 to 24 carbon atoms. Such a composition would contain up to 10% of the polyglycerol component and 5% water.
It is another object of this invention to make a microemulsion which is free of a co-surfactant, such as an alcohol or acid.